{mosimage}Dear EarthTalk: Is it true that the carcasses of whales that wash up on shore are considered dangerous to humans because of the amount of toxins and chemicals in their blubber?

-- Michael O’Loughlin, Tigard, Ore.

Whether wildlife officials in a given region consider a dead, beached whale a biohazard or not is a local decision; however, experts agree that only trained professionals should go anywhere near a dead wild animal to prevent the spread of bacterial infection, no matter whether any industrial pollutants might be oozing out. Regardless, it is true that some types of whales, given their spot at the top of the marine food chain, do harbor chemical pollution in their fatty tissue and organs.

Researchers have found, for instance, that PCBs, dangerous toxins notorious for polluting New York’s Hudson River and long banned in the U.S., are present in the blubber of beluga and orca whales, among others, in amounts - some 80 parts per million - that could kill a person. DDT, a pesticide banned in 1972 in the U.S. for wreaking havoc on bird and other wildlife populations, also still shows up in measurable amounts in whale blubber around the world.

Beyond such well-known pollutants, newer ones are starting to show up in large amounts in the carcasses of beached whales and other top marine predators. Today, biologists are most worried about the marked increase in flame retardants (PBDEs) and stain repellents (PFOs) in dead marine mammals. Flame retardants are particularly troublesome because they “seem to travel over long distances in the atmosphere, and some studies have shown that they can be toxic to the immune system and can affect neurobehavioral development,” according to a recent report by the Arctic Council, a multilateral international body in charge of overseeing Arctic law and development. The report also notes that PFOs do “not seem to break down under any circumstances,” meaning they are passed up the food chain to whales and other top predators, and then in some cases consumed by humans, especially indigenous Arctic people still hunting marine animals as part of their subsistent lifestyles.

According to the Humane Society of the U.S. (HSUS), whales aren’t the only wild animals carrying around large amounts of toxic chemicals. Bottle-nosed dolphins, manatees, polar bears, seals, sea lions and other marine wildlife also have PCBs, DDT, PBDEs, PFOs and the other pollutants in their tissue and blood streams.

“The large-scale die-off of bottle-nosed dolphins along the mid-Atlantic coast of the United States in the mid-1980s may have been the direct or indirect result of increasing levels of toxic waste from industrial sources,” HSUS reports, adding that “such pollutants can depress the immune system of marine mammals, making the animals susceptible to diseases they could normally fight off.”

Environmental and health experts worry about such contamination because many of the chemicals in question are known “endocrine disruptors,” meaning they can impair reproduction in both wildlife and humans by mimicking or altering natural hormonal activity. Such chemicals can also cause neurological problems and developmental or skeletal abnormalities.